Hong Kong is one of the most dynamic and advanced cities in the world and depends upon a highly sophisticated network of power lines to keep its high-rise urban areas buzzing around the clock.

The city’s largest integrated power utility CLP Power operates more than 16,800 kilometers of high-voltage, long-distance transmission power lines, around one-third of them are overhead transmission lines criss-crossing vast tracts of the city’s open countryside. 

Those exposed power lines need constant monitoring and pruning to prevent damage from overgrown trees or trees brought down by storms in an era of climate change and increasingly unpredictable weather patterns. It is essential for CLP Power to keep the overhead towers carrying power cables in good condition to maintain a reliable electricity supply, while minimising impact on the environment.

The responsibility for that work falls on the shoulders of the company’s Vegetation Management Team established in 2001. The team’s leader YL Tang says: “With climate change causing more super typhoons, we expect there to be more catastrophic failures caused by extreme weather conditions, posing a threat to our power distribution.”

Every tree counts

Working with Research Chair Professor of Geography and Environmental Science at the Education University of Hong Kong Jim Chi-yung, Tang’s team in April 2022 introduced a new system for predicting the growth rate of trees, helping identify risky trees near overhead cables and reduce operating costs.

CLP Power Director for the North Region Mr Michael Lau says the new system has substantially strengthened the company’s vegetation management capability and improved work efficiency. 

More than 200 species – including kapok, camphor, bauhinia, and Chinese banyan – have been identified along the power grids in the New Territories, Lantau Island, and parts of Kowloon, amounting to about half of the tree species documented in the city.

Ten tree species, such as bauhinias, Chinese banyan, and red cotton trees, were selected in 2019 for sampling, and the project team recorded the trees’ positions, length, and number of branches to develop the database of the system. 

The system also uses real-time data from the Hong Kong Observatory, such as temperatures, precipitation, and sunlight to forecast the growth speed of trees. In addition, with the GPS function embedded in the system, CLP Power’s Vegetation Management Team is now able to track the exact location of the trees and update its records more efficiently.

Planting right trees

Professor Jim, who is popularly known as the “Tree Professor” for his enthusiasm in tree conservation, says the system can precisely forecast the growth speed of trees and identify fast-growing species. “By avoiding planting fast-growing species, we can help reduce the pruning needs and the risk of damaging nearby overhead cables”, he says. 

Meanwhile, Tang highlights the importance of mitigating potential risks from overgrown trees to power supply reliability. “When overgrown trees touch overhead cables, it can cause voltage instability, leading to light flickering. Additionally, some risky trees that might not be close can still damage cables if their branches fall off,” he explains.    

The company has also been working on integrating the image data captured by drones using Artificial Intelligence technology to enhance vegetation management, making it easier to predict any imminent risks.  

Tang’s team has discovered that nearly 70% of overhead line pole failures are caused by falling trees. Fast growing, invasive, and exotic trees such as white popinac, acacia, and Brisbane box are particularly brittle and prone to toppling in strong winds.

“We could have simply cut down the trees, but we are committed to caring for the environment, which is one of the corporate values of CLP,” Tang explains. 

“This motivates us to work harder with field experts to strike a balance between maintaining our overhead line systems and keeping trees in rural areas of Hong Kong through more efficient pruning and monitoring work.”

Blossoming benefits 

The company has developed a strategy of integrated vegetation management – an innovative approach for dealing with overhead line corridors. This includes more focused pruning and growing attractive native tree species, such as Hong Kong hawthorn and sweet viburnum, with manageable heights and limited maintenance to support biodiversity. 

CLP Power’s sensitive and proactive approach is a blueprint for other public utility companies to follow, balancing the need for a safe and reliable power supply with a responsibility for protecting Hong Kong’s countryside and its rich biodiversity.